1. Field of the Invention
The present invention relates generally to a resin product and a process for producing the same, more particularly a resin product in which a plating layer is formed only at the required portions on the surface of a resin base material, with a coating layer being formed partly or entirely on the rest of the portions which are defined by the edges of the plating layer.
2. Description of the Related Art
It has generally been proposed to form front grilles of automobiles with resins and to decorate them using plating techniques.
Known techniques are shown in Japanese Examined Patent Publication No. 45-37843 and Japanese Unexamined Patent Publication Nos. 55-152195 and 52-50937. In one of these techniques, as shown in FIG. 26, a contoured groove 72 having a substantially V-shaped cross section is defined on the surface of a base material 71 along the boundary between the to-be-plated or to-be-decorated portion (left side in FIG. 26) and the to-be-unplated portion (right side in FIG. 26). The base material 71 is first subjected to chemical plating, whereby to form a chemical plating layer 73 on the entire surface of the base material 71 except for the bottom 72a of the groove 72. Since the bottom 72a of the groove 72 is too narrow to allow a plating solution to intrude thereon, the chemical plating cannot substantially be applied to the bottom 72a.
The base material 71 having the chemical plating layer 73 formed thereon is then subjected to an electroplating step, as shown in FIG. 27. The base material 71 is first immersed in a predetermined electroplating solution, and then the chemical plating layer 73 formed on the to-be-plated portion is electrically charged to allow an electroplating layer 74 to be formed thereon. The chemical plating layer 73 formed on the to-be-unplated portion is electrically insulated by the presence of the groove 72, so that the chemical plating layer 73 is dissolved by the electroplating solution and removed from the base material 71. Thus, the chemical plating layer 73 and the electroplating layer 74 can be formed on the base material 71 only at the portions where decorative plating is required.
The above-described technique can be applied when automotive exterior resin equipments such as front grilles and back panels are produced. For example, in the case of front grille, a plating layer is formed on the front surface of a front grille base material at predetermined portions, and a coating layer is formed on the rest of the portions (on the front surface). Such front grille can be produced, for example, in the following manner.
First, a front grille base material with a plating layer formed partly thereon is prepared. The portions where the plating layer should remain as such are covered with an electroforming mask. The portions which are not covered with the electroforming mask (exposed portions) are coated with a predetermined coating material by means of spraying. The coating material is dried to form a coating layer. The electroforming mask is then removed to provide a front grille.
However, in the prior art technique described above, the size of the groove 72 is relatively small. Accordingly, it is very difficult to position the electroforming mask on the base material 71 in such a way that the edges of the electroforming mask may accurately be aligned with the edges of the plating layer. Thus, when a coating layer is formed, the boundary between the coating layer and the plating layer tends to be unclear, which diminishes the appearance of the resulting product.
In such cases where the plating layer fails to be fully covered with the electroforming mask, the coating layer is liable only to be partly formed on the plating layer. Accordingly, when a general-purpose coating material (a coating material in which consideration is given only to the adhesion with the base material) is selected and applied, the coating layer tends to separate from the plating layer.